can't think happy positive thoughts no matter what it seems :(

I cannot seem to be happy. I'm constantly thinking that something is going to be wrong with my pregnancy. Keep thinking I won't make it. Keep thinking that I will have a miscarriage. It's like I can't even look forward to the future because I assume that I will miscarry. I keep thinking everything I feel is wrong when I know I'm doing okay. Im just not sure why all my thoughts are bad :(